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Biology A level > Required practicals > Flashcards

Required practicals Flashcards

1
Q

RP2- Calculating mitotic index of root cells.
Why is the onion/ garlic bulb suspended in water?

A

To stimulate cell division

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2
Q

RP2- Calculating mitotic index of root cells.
Why is root tip placed in ethanoic alcohol?

A

To stabilise the chromosomes

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3
Q

RP2- Calculating mitotic index of root cells.
Why is root tip placed in HCL and heated for 5 mins at 60 degrees

A

Helps separate cells by breaking down intracellular molecules

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4
Q

RP2- Calculating mitotic index of root cells.
Why are roots rinsed in water for 5 mins

A

To remove any HCL- ensuring chromosomes are not damaged

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5
Q

RP2- Calculating mitotic index of root cells.
Why are root tips pushed hard down on and why can no sliding occur

A

To ensure light can penetrate the cells- thin layer
Sliding will damage chromosomes

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6
Q

RP1- Investigation into the effect of a named variable on the rate of enzyme-controlled reaction
How will temperature be maintained

A

Use a thermostatically controlled water bath

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7
Q

RP1- Investigation into the effect of a named variable on the rate of enzyme-controlled reaction
How will amount of enzyme be controlled?

A

Use enzyme solutions of known concerntrations
Keep enzymes in same favourable conditions when storing

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8
Q

RP3- Production of a dilution series of a solute to produce a calibration curve to identify the water potential of plant tissue
Why can’t chips be too large?

A

Wont fit into tubes

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9
Q

RP3- Production of a dilution series of a solute to produce a calibration curve to identify the water potential of plant tissue
Why cant chips be too small?

A

Small inaccuracies are a higher proportion when dimensions are small

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10
Q

Calculating degrees of freedom Chi squared

A

Number of classes-1

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11
Q

Degrees of freedom Student T test

A

(n1-1) + (n2-1)

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12
Q

RP4- Investigation into named variable on cell membrane permeability
Why is beetroot washed before being added?

A

Removes pigment from damaged cells
Only pigment that leaves cells via membranes will be measured

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13
Q

RP4- Investigation into named variable on cell membrane permeability
Suggest why cylinders are 65 mm long

A

Enough cells to detect change in pigment
Not too big that beetroot wouldnt fit

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14
Q

RP4- Investigation into named variable on cell membrane permeability
Suggest why 25 cm^3 of water is added to each test tube

A

Enough to cover all beetroot cells
Not too much that the pigment is very diluted

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15
Q

RP4- Investigation into named variable on cell membrane permeability
Suggest why 25 cm^3 of water is added to each test tube

A

Enough to cover all beetroot cells
Not too much that the pigment is very diluted

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16
Q

RP5: Dissection of animal or plant gas exchange or mass transport system or of organ within such a system

How to reduce injury / infection

A

Cut away from body
When holding sharp items- hold downwards
Ensure to sterilise equipment after use

17
Q

RP6- Effect of antimicrobial substances on microbial growth

Name some aseptic techniques

A

Wearing goggles and labcoats
Use bleach to clear area
Keep petri dish closed as much as possible
Use flame to sterlise equipment before use
Wash hands

18
Q

RP6- Effect of antimicrobial substances on microbial growth

Why is mouth of beaker put in flame

A

The heat creates a convection current which drives air away from the bottle
Prevents air bourne microorganisms from entering

19
Q

RP6- Effect of antimicrobial substances on microbial growth

Why is blue flame used rather than a yellow flame?

A

Blue flame is hotter-hot enough to kill microorganisms and cause air to move ou of bottle

20
Q

RP6- Effect of antimicrobial substances on microbial growth

How does incubating dishes at room temperature reduce danger

A

Prevents growth of organisms which thrive at body temperature
Reduces chance of pathogenic bacteria forming

21
Q

RP6- Effect of antimicrobial substances on microbial growth

What would make a suitable control experiment

A

Repeat paper disks soaked in water
Proves that it is antibiotic which kills the bacteria

22
Q

RP6- Effect of antimicrobial substances on microbial growth

What needs to be controlled so that the results can be compared

A

Concentration of nutrients in agar
Temperature and pH
SPecies of bacteria
Time plates are left for
Concentration of antibiotics

23
Q

RP8- The effect of wavelength of light on dehydrogenase activity in chloroplasts

What is the purpose of container of water between the lamp and experimental tubes

A

Acts as a heat sink
Prevents rate of reaction in tubes being affected by temperature
Prevents Enzymes from being denature

24
Q

RP9- Investigation into the effect of a named variable on rate of respiration

What volume of water is ideal to use for water bath

A

1dm
Loses heat slowest
Needs water added less often

25
Q

RP9- Investigation into the effect of a named variable on rate of respiration

Two solutions initially kept separate
Why?

A

Ensures whole reaction happens at measured temperature
Allows each solution to get to temperature

26
Q

RP10- Investigation into the effect of an environmental factor on movement of an animal

Why is a teaspoon used to move woodlice instead of tweezers?

A

Tweezers unethical
May injure woodlice affectinng results

27
Q

RP10- Investigation into the effect of an environmental factor on movement of an animal

Why does filter paper have to be replaced after each experiment

A

Woodlice may leave a residue which could affect the movement of the other woodlice in next experiment

28
Q

RP10- Investigation into the effect of an environmental factor on movement of an animal

Why are woodlice replaced after each experiment

A

Different woodlice respond in differenrt ways
Ensures any anomalies have little effect on the results

29
Q

RP12- Investigation into the effect of a named factor on the distribution of a living species

Why are quadrats placed randomly?

A

To ensure there was no bias
To ensure the results were representative of the sample

30
Q

RP12- Investigation into the effect of a named factor on the distribution of a living species

What is a quadrat

A

A line over which measurements are made over several positions

31
Q

Equation for dilution series volume

A

Volume of current stock=(final conc. neededXfinal volume needed)/initial concentration

Biology A level (13 decks)

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